Means for controlling excitation of boosters or generator-fields.



Patented Sept. ll, I900.

J. APPLETON.

MEANS FOR CONTROLLING EXCITATION OF BOOSTERS OR GENERATOR FIELDS.

(Application flied Mn. 30, 1899.)

2 Shoets$haet 1.

(No Model.)

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wkmu zm Patented Sept. ll, I900.

- J. APPLETON. v

MEANS FOR CONTROLLING EXCITATION OF BOOSTERS OR GENERATOR FIELDS.

(Application filed Mar. 30. 1899.,

2 Sheets-Sheet 2,

(No Model.)

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UNITED STATES PATENT OEFIcE.

JOSEPH APPLETON, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THE ELECTRICSTORAGE BATTERY COMPANY, OF GLOUCESTER CITY, NEIV JERSEY;

MEANS FOR CONTROLLING EXCITATION 20F BOOSTERS OR GENERATOR-FIELDS.

SPECIFICATION forming part of Letters Patent No. 657,722, datedSeptember 11, 1900.

Application filed March 30,1899. Serial No. 711,131. (No model.)

T0 aZZ whom, it may concern.-

Be it known that LJosnrn APPLETON,a subject of Her Majesty the Queen ofGreat Britain, residing at the city of Philadelphia, in the county ofPhiladelphia and State of Pennsylvania, have invented certain new anduse ful Means for Controlling the Excitation of Boosters orGenerator-Fields, of which the following is a specification.

One object of the invention is to efficiently control the excitation ofa booster or generator-field by means of a comparatively-smallresistance and in such manner that the strength of the field may bevaried from maximum to Zero and also, if required, reversed in polaritywithout opening the field-circuit.

To this and other ends my invention, stated in general terms, comprisesa resistance or resistances connected across any available source ofcurrent which will give an approximatelyconstant current and todifierent points of which the field-coil of the machine is connected,whereby the difference of potential at its terminus is varied, incontradistiuction to the interposition in series with the field-coil ofa resistance large enough to choke the current, and thus vary the fieldstrength.

My invention further consists of the improvements which are hereinafterdescribed and claimed.

The nature, characteristic features, and scope of my invention will bemore fully understood from the following description,taken in connectionwith the accompanying drawings, forming part hereof, and in which-Figure 1 is a view illustrating means embodying features of my inventionand constructed to vary the field strength of a machine from zero to itsmaximum. Fig. 2 isa View showinglike means constructed not only to varythe field strength, but also to reverse the polarity; and Fig. 3 is adiagrammatic view illustrative of the construction and arrangement ofthe apparatus shown in Fig. 2.

In the drawings, 1 is the field-coil of a dynamo-electric machine orbooster of which the field strength is to be varied. dis the armaturethereof, and it is in series with the loattery B. These two areconnected in multiplearc relation with the load-circuit L and maingenerator G. 1

different points of the resistance for purposes ;to behereinafterdescribed. 8 and 9 are stops that may be employed forarresting the arm 6, and thus limiting its range of travel.

2 and 3 indicate the leads from a source of current used to effect andvary the excitation of the field-coil 1. This source should not be thearmature d, because there may not be in it the requisite voltage andpolarity upon which to build the required excitation in thefield-coil 1. As shown the source availed of is the battery B.

Referring to Fig. 1, R is a rheostat provided with subdivided resistance4, having contacts 5, and with a movable arm 6, having a contact 7. Therheostat is provided with three terminals or binding-posts 11, 12, and13, of which, two, 11 and 13, are adapted for connection with the leads2 and 8 and include between them the whole of the resistance, and ofwhich the other, 12, is adapted for con noction by way of the arm 6 andcontact '7 with 14 and 15 are conductors for connecting the ends of thecoil 1 with the terminals 11 and 12. Between the ends of the resistance4 there is a certain difference of potential. For example and forclearness of explanation it will be assumed that there is a potential offive hundred volts between the left-hand and right-hand ends of theresistance. This is indicated upon the drawings by reference to thecharacters 500 volts and 0 volts, so that between the right-hand end ofthe re sistance and the successive contacts 5, proceeding in a clockwisedirection, there are gradually-increasin g differences in potential. Ifthe contact-arm 6 were turned toward the, right until it rested upon theextreme righthand position, there would be a difference of potential offive hundred volts between the ends of the coil 1, or, in other words,between the conductor lei and the conductor 15. This is the maxim umdifference in potential, so that the strength of the field-coil 1 wouldunder these circumstances be atits maximum. As the arm 6 is turned in acounter-clockwise direction over the contacts 5 it reaches pointsbetween which and the extreme left-hand end there is less and lessdifference of potential, thus diminishing the strength of the field-coiluntil finally in its extreme left-hand position a err/.722

it rests upon the extreme left-hand contact, and undersuch circumstancesthere is no difference in potential and the strength of the field-coilis zero. There are branch paths between 2 and 3 for the current. Onebranch includes the conductor 14, the field-coil 1, the conductor 15,and the arm 6. The other branch in eludes more or less of the resistance4:, according to the position of the arm 6. As shown, it includes somuch of the resistance as lies between the terminal 11 and the end 7 ofthe arm. The rest of the resistance might be regarded as a continuationof the lead 3.

Referring now to Figs. 2 and 3, in which the strength of the field-coilis not only varied, but is also reversed as to its polarity, I willfirst refer to Fig. 3, which is a diagrammatic representation of thearrangement of Fig. 2. In this figure 9" and 7" represent similarportions of the resistance, and each of them is subdivided and providedwith contacts. Between the ends of each of these portions 1" and r ofresistance there is a certain difference of potential, and it will beassumed to be five hundred volts and indicated by the referencecharacters 500 volts, 250volts, and 0 volts. However, this difference inpotential is in opposite directions in the two portions r and r ofresistance. For example, the portion 0* of resistance is connectedacross the leads 2 and 3 and the portion 7' of resistance is connectedacross the leads by means of crossed conductors 18 and 19. Thedifference in potential between the portion 7" of resistance and theportion r of resistance at the left-hand end is five hundred volts inone direction, and at the right-hand end it is five hundred volts in theother direction, and at the middle points it is nothing. The fieldcoil 1is connected by conductors 10 and 17 with conducting-strips c and c, andthere is amovable arm ct, whose ends a and a are adapted to bridge andcarry current from the contacts of the resistances r and r to theconducting-strips c and c',respectively. Each of the ends a and a shouldbe wide enough to span two of the contacts of the resistance, so as toprevent breaking the circuit when they are shifted. When the arm a is inits extreme left-hand position, the field-coil l is connected across theresistances r and 0' at points of maximum difference in potential in onedirection which may be indicated by the arrow 20, and the strength ofthe field-coil is therefore at its maximum in that direction. As the arma is shifted toward the right it operates to connect the field-coil 1across points of the resistances between which the difference inpotential is less, until finally when the arm occupies its centralposition the field-coil 1 is connected across points of the tworesistances r and r between which there is no difference in potential.Consequently no current traverses the field-coil, and its strength iszero. Under these circumstances the circuit through the field-coil isfrom 2, through more or less of the resist ance r, to a, to c, to 16,through 1., to 17, to 0, through more or less of the resistance W, by19, to 3. There are also two other paths for the current through theresistances r and r When the arm a is shifted from its intermediateposition toward the right and as it moves from contact to contact, itincludes the coil 1, across points of the resistance r and r betweenwhich there is an increasing difference of potential, until finally whenthe arm reaches its extreme right-hand position it connects the coil 1across points of ma.\"imum difference of potential. However, under thesecircumstances the current traverses the coil 1 in a direction that maybe indicated by the arrow 21, so that the polarity of the field isreversed. When the arm a is be tween the center line and the right-handend of the resistances 9" and T the circuit through the field-coil is byway of 18, more or less of resistance 7*, a 0, 1'7, coil 1, 16, c, a,more or less of the resistance a", to 3. There are also other paths byway of the resistances i" and r for the current. Referring now to Fig.2,

the subdivisions of the resistance have their contacts arranged incircular form and the arm a is pivoted, which renders the crossoverconnections 18 and 1f) unnecessary and causes the parts to assume theappearance of an ordinary rheostat r. In Fig. 2, and following the sameassumptions as to voltage, the difference in potential between the endsof the subdivision of resistance a" and also the resistance r is fivehundred volts. The difference in potential between the righthand end ofthe resistance 0" and its middle point is two hundred and fifty volts,and the same is true of the resistance 7' so that in the position shownthe field-coil 1 is con-- nected across points of the resistance a" andthe resistance 1' between which there is no difference in potential.Consequently the strength of the field-coil is zero. When the arm a isturned from the position shown in the drawings in a counter-clockwisedirection, it connects the field-coil 1 across points of the resistancesr and 1' of increasing differences of potential, so that the strength ofthe field 1 is gradually increased in one direction, and when the arm aoccupies the position indicated by the dotted line 22 23,poi nts ofmaximum difference of potential are connected by it through the coil 1,of which the strength is then at its maximum in the other direction. Thecircuit of the ficld-coil 1 under these circumstances is from 2 throughmore or less of the resistance r, by ct, to c, to 10, through 1 "(0-17,to c, by (6 through more or less of the iesistance r by 19, to 3.Ourrent is also traversing the resistances r" and r When the arm a isturned in a clockwise direction out of the position shown in Fig. 2, thestrength of the coil 1 is gradually increased, but in the otherdirection, because it is connected across points of the resistances rand r between which there is an increasing difierenco of potential,until, finally,when

IIO

the arm it reaches the position indicated by the dotted line 24 25 thecoil 1 is connected across points of the resistances r and r betweenwhich there is a maximum difference in potential, and consequently amaximum strength in the field-coil 1. Under these circumstances thecircuit of the coil 1 is from 2, by 18, through more or less of theresistance 1*, by o by c, to 17, through coil 1 to 16, by c, to a,through more or less of the resistance r to 3. Inasmuch as the functionof the resistance is to furnish various points between which there aredifferences of potential and across which the field-coil is connected atdifferent points, it follows that it may be very much smaller than wouldbe required if it were placed in series with the coil and used to varyits strength by choking more or less of the current.

It will be obvious to those skilled in the art to which my inventionrelates that modifications may be made in details without departing fromthe spirit thereof. Hence I do not limit myself to the preciseconstruction and arrangement of parts hereinabove set forth,

and illustrated in the accompanying drawings; but,

Having thus described the nature and objects of my invention, what Iclaim as new, and desire to secure by Letters Patent, is

1. Means for controlling the excitation of the field of adynamo-electric machine or booster which comprise a source of currentother than said dynamo or booster, and a resistance connected acrosssaid source of current and to difierent points of which the field coilis connected, substantially as described.

2. Means for controlling the excitation of the field-coil of adynamo-electric machine or booster which comprise a source of currentother than said dynamo or booster, a pair of resistances connectedacross said source of current, and means for connecting the terminals ofthe field-coil to various points of the same, to vary both potential andpolarity of the field, substantially as described.

JOSEPH APPLETON.

Witnesses:

A. B. STOUGHTON, THEODORA HESSER.

